About Jason Thibeault

Hi! I'm a tech guy, skeptic, feminist, gamer and atheist, and love OSS and science of all stripes. I enjoy a good bit of whargarbl now and again, and will occasionally even seek it out. I am also apparently responsible for the death of common sense on the internet. My bad.

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Global warming does not improve plant productivity

There’s a very short window where plants improve with more CO2, where they scrub more of it from the atmosphere than usual. This window is apparently overwhelmed in a hurry with the levels we’re seeing, though, resulting in crop die-outs which are exacerbated by warming-influenced droughts.

This would, in a perfect world, shut up those science denialists who admit global warming is happening, but think plants are going to fix it all for us. Considering we’re waging an all-out war on plants to begin with, I fail to see how these people honestly think there’s not a problem. It’s either short-sightedness or wishful thinking that leads people to believe this particular line of anti-AGW bunkum.

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About the author

Hi! I'm a tech guy, skeptic, feminist, gamer and atheist, and love OSS and science of all stripes. I enjoy a good bit of whargarbl now and again, and will occasionally even seek it out. I am also apparently responsible for the death of common sense on the internet. My bad.

I have opinions. So do you. You want to share them with me. I would like to do likewise. Please don't expect a platform for proselytizing that will go unchecked and unchallenged, though. Contact me via the clicky thingies under my banner.

The commenting rules are simple: don't piss me off. This rule has worked for me for a decade; I have never found a need for any other rule, because any other rules leads to rules-lawyering. Just remember -- this is my property, not yours.

15 thoughts on “Global warming does not improve plant productivity”

Not to mention the effect of being in a different climate has on plants.

For example, the tree line vs. altitude happens for a reason. Just a few feet over and the trees can’t grow. Most climate boundaries aren’t that clear but there is so much more than just CO2 levels in the equation.

Plants fixing global warming is the same thing as jebus saving our “souls” is the same thing as capitalism solving all economic ills. Those are simple answers to complex problems, and, in all cases, completely wrong. But many people like simple solutions since they fit on placards or put on a picture and posted to facebook.

As a plant biochemist, especially one who used to work in a lab which studied the effects of elevated CO2 on plant photosynthetic rates, then I can certainly tell you that any increases in instantaneous photosynthetic rates are transitory. After a few days, the plants become essentially carbon saturated, and photosynthetic rates are depressed. Of course, most plants in most environments are nitrogen, not carbon, limited (which is why farmers spread ammonium nitrate on their plants, and not glucose!). Elevated CO2 levels may, however, lead to better water use efficiency, increased resistance to toxins (less accumulation in leaves, as stomata are open less of the time (and less open), decreasing transpiration rates (and hence the accumulation of toxins taken up from groundwater in leaves, etc)). We expect also changes in soil carbon fluxes, as plants pump more carbon to the roots, which is exuded as root exudates, phosphatases, etc, which the soil bacteria gobble up, respiring away as they do. In itself, that shouldn’t be too much of a problem, but it can lead to alterations in soil structure, and may lead to other, unforeseen circumstances. Really, it’s very unclear what will happen in the long term, but these “quick fix” ideas of right wing politicians are completely at odds with reality.

C3 plants should have a distinct advantage. C4 plants expend a bit of energy to pump CO2 into the bundle sheath cells (where CO2 fixation by Rubisco takes place). Maintaining a high CO2 concentration inside the bundle sheath cells allows them to also minimise photorespiratory “waste” (of both C and N). However, as mentioned, studies suggest that the photosynthetic rate of C3s will downregulate after a few days or weeks, so maybe these “energetic” considerations are not so important.

What I think is important is that elevated CO2 levels lead to reduced stomatal aperture in C3 plants, which means that they are able to conserve water more efficiently. Obviously, that will have a big effect in areas with marginal water sufficiency. (although it may cause other problems. Ultimately, the world is too big, complex, and heterogeneous to predict in a simple way what will happen to plants in different areas. However, one thing we can say is that increases in photosynthetic rates tend to be transitory, simply because plants have limited sink strength.

I’m curious if the idea that CO2 increases will just make plants work harder and scrub more out of the atmosphere is a common one. I don’t think I have heard this argument before.

It seems to me to be a pretty insidious idea, because it sounds totally reasonable on the surface that plants would work harder with more CO2 available. The idea that the plants will therefore fix the problem sounds like an overreach, but if someone has already accepted the first part as reasonable they might not think too hard about the second part.